Stand-alone integrated water treatment system for distributed water supply to small communities

ABSTRACT

Provided is a standalone integrated water treatment system for a distributed water supply. A filter input receives water to be treated. A coagulation system is in operative connection with the filter input, wherein the water which has been filtered is subjected to a coagulation process performed by the coagulation system to create pin floc from suspensions in the water. A maturation buffer tank is in operative connection with the coagulation system, wherein floc is aggregated in size within the water. A spiral separator is in operative connection with the maturation buffer tank, and the water is separated into two water streams, a first stream of water having most of the floc removed, and a second stream of water which includes a concentrated amount of the floc. An optional filtration system is in operative connection with the spiral separator and is configured to receive the first stream of water and to perform a filtration operation on the first stream of water. A sterilization system is in operative connection with the optional filtration system and is configured to perform a sterilization operation on the first stream of water. The water is then output from the sterilization system as potable water.

CROSS REFERENCE TO RELATED PATENTS AND APPLICATIONS

Cross Reference is hereby made to related patent applications, U.S.patent application Ser. No. 12/484,058, filed Jun. 12, 2009 (nowpublished as US2010-0314327A1), by Lean et al., entitled, “PlatformTechnology For Industrial Separations”; U.S. patent application Ser. No.12/484,005, filed Jun. 12, 2009 (now published as US-2010-0314325-A1, byLean et al., entitled, “Spiral Mixer for Floc Conditioning”; and U.S.patent application Ser. No. 12/484,071, filed Jun. 12, 2009 (nowpublished as US-2010-0314323-A1), by Lean et al., entitled, “Method andApparatus For Continuous Flow Membrane-Less Algae Dewatering”, thespecifications of which are each incorporated by reference herein intheir entirety.

BACKGROUND

Clean water is an increasingly scarce commodity in the world and isparticularly an acute issue in the developing world. Most contemporarywater treatment systems require a complex, expensive infrastructure,including large installations, chemical supply and storage facilities,electrical energy and machinery to support communal water treatment,such infrastructure is often not available for small communities.

INCORPORATION BY REFERENCE

U.S. Patent Application Publication No. 2008-0128331-A1, published Jun.5, 2008, entitled, “Particle Separation And Concentration System”; U.S.Patent Application Publication No. 2009-0114607A1, published on May 7,2009, entitled, “Fluidic Device And Method For Separation Of NeutrallyBuoyant Particles”; U.S. Patent Application Publication No.09-0114601-A1, published May 7, 2009, entitled, “Device And Method ForDynamic Processing And Water Purification”; U.S. patent application Ser.No. 12/120,093, filed May 13, 2008, entitled, “Fluidic Structures ForMembraneless Particle Separation”; U.S. patent application Ser. No.12/120,153, filed May 13, 2008, entitled, “Method And Apparatus ForSplitting Fluid Flow In A Membraneless Particle Separator System; U.S.patent application Ser. No. 12/234,373, filed Sep. 19, 2008, entitled,“Method And System For Seeding With Mature Floc To AccelerateAggregation In A Water Treatment Process”; U.S. patent application Ser.No. 12/484,071, filed Jun. 12, 2009 (now published asUS-2010-0314323-A1), entitled, “Method And Apparatus For Continuous FlowMembrane-Less Algae Dewatering”; U.S. patent application Ser. No.12/484,005, filed Jun. 12, 2009 (now published as US-2010-0314325-A1,entitled, “Spiral Mixer For Floc Conditioning”; U.S. patent applicationSer. No. 12/484,058, filed Jun. 12, 2009 (now published asUS2010-0314327A1), entitled, “Platform Technology For IndustrialSeparations”, all naming Lean et al. as inventors; and U.S. Pat. No.7,160,025, issued Jan. 9, 2007, and entitled Micromixer Apparatus AndMethod Of Using Same”, to Ji et al.; are each hereby incorporated byreference in their entirety.

BRIEF DESCRIPTION

Provided is a standalone integrated water treatment system for adistributed water supply. A filter input receives water to be treated. Acoagulation system is in operative connection with the filter input,wherein the water which has been filtered is subjected to a coagulationprocess performed by the coagulation system to create pin floc in thewater. A maturation buffer tank is in operative connection with thecoagulation system, wherein pin floc grows by aggregation to exceed theseparable size within the water. A spiral separator is in operativeconnection with the maturation buffer tank, and the water is separatedinto two water streams, a first stream of water having most of the flocremoved, and a second stream of water which includes a concentratedamount of the floc. An optional filtration step is in operativeconnection to the spiral separator and is used to treat the first streamof water. A sterilization system is in operative connection with thefiltration device, if present, and is configured to receive the firststream of water and to perform a sterilization operation on the firststream of water. The water is then output from the sterilization systemas potable water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram of a standalone integrated watertreatment system for distributed water supply in accordance with theconcepts of the present application;

FIG. 2 provides a more detailed figure depicting the operation of anelectrocoagulation system;

FIG. 3 is a graphic illustration of a fluid channel;

FIGS. 4A and 4B are graphs illustrating a velocity profile and apressure profile;

FIG. 5 is an illustration of one form of a fluid separation deviceaccording to the presently described embodiments;

FIG. 6 is another illustration of the fluid separation device of FIG. 5;

FIG. 7 is a representation of a neutrally buoyant particle flowingthrough a channel and forces acting thereon;

FIG. 8 sets forth a perspective cutaway view of an ultravioletsterilization system which may be used in the system of the presentapplication;

FIG. 9 illustrates an embodiment of a standalone integrated watertreatment system for distributed water supply according to the conceptsof the present application; and

FIG. 10 illustrates another embodiment of a standalone integrated watertreatment system for distributed water supply according to the conceptsof the present application.

DETAILED DESCRIPTION

FIG. 1 is a block diagram illustrating a standalone integrated watertreatment system 100 according to the concepts of the presentapplication. Input water 102 from a base water source such as a pond,creek, river, lake, estuary, well, holding tank or other location isprovided to system 100 at a filtration/screened input where openings ofan input filter/screen arrangement 104 are sized such as to trapparticulates above a certain size (e.g., the openings may be sized toblock particulates sized larger than 2 mm or 5 mm, depending on theimplementation). The screened water is then passed to anelectrocoagulation (EC) system 106 designed to act upon the water toremove undesirable suspended solids by creating (small) pin floc. Thepin floc laden water is then provided to a maturation buffer tank 108where particulates are further aggregated to form more mature (larger)floc. In particular, the buffer tank includes a mixing protocol forfaster floc formation. Following an appropriate maturation time, thewater with the formed floc material, is passed to a spiral separator110. The spiral separator 110 is designed to separate out floc above acertain size from the water. Thereafter, the stream of water from whichthe floc has been removed is passed through an optional filter 112before proceeding through an ultraviolet (UV) sterilization system 114.The stream of the water having the separated floc, i.e., the water notpassed to the filter or UV sterilization system 114, is passed out ofsystem 100 to a waste stream or holding tank 116.

The optionally provided final filtration/screening arrangement 112,removes particulates which may have passed accidentally through thepreceding processes. The filter can be selected to satisfy U.S.Environmental Protection Agency (EPA) mandates with granular mediafilters (GMF), as well as other environmental requirements of othercountries. The water quality immediately after separation may alreadyexceed regulatory standards in which case, the filter acts as aninsurance against abnormal periods of operation such as flow pulsationor sudden spikes in turbidity of the source water. At UV sterilizationsystem 114, microorganisms in water 102 are either sterilized or killed.The water is then output as potable water 118.

In the embodiment of FIG. 1, power for operation of system 100 isprovided by a solar or photovoltaic (PV) system arrangement 120. Inalternative embodiments, electrocoagulation system 116 and maturationbuffer tank 118 are integrated into a single unit having the buffer tankas a post electrocoagulation process chamber, and/or spiral separator110 and UV sterilization system 112 are integrated into a single unit.In another embodiment the UV system can be extended to perform advancedoxidation of source water contaminants, e.g. by exposing the sourcewater to a UV active surface area coated with a photoactive materialsuch as TiO₂, or other appropriate material. The TiO₂ serves as aphotocatalyst for the UV and, if applied as a nanocoating on the fluidbearing surfaces of spiral separator 110 also acts as an anti-foulingagent that minimizes bio-film formation. Alternatively, the TiO₂ mayalso be dispersed within the water in the form of nano particles andrecovered by spiral separation after the UV sterilization process.Volume dispersion of the TiO₂ results in more efficient photocatalysisbut this practice is not common due to the need for membranes to recoverthe dispersion. The spiral separator 110 has been shown to effectivelyrecover TiO₂ dispersions which have been aggregated through somechemical modification such as pH adjustment or coagulant and so forth.Thus, in FIG. 1 the UV sterilization block 114 may be implemented as astandalone device, or incorporated into the spiral separator 110.Additional advanced oxidation capability can be integrated either as acoating on the inside surface of spiral separator 110, as TiO₂ dispersedwithin the water or as a combination of the foregoing. Thus in certainembodiments, sterilization may occur before an optional filteringprocess.

It is appreciated in certain embodiments pumping units are used to movethe water from various components of system 100, e.g., input water 102may be pumped into system 100, as well as into or out of the system'scomponents, such as from electrocoagulation module 106 to maturationbuffer tank 108, and from the buffer tank 108 to spiral separator 110,as well as between and/or through other components of system 100.Alternatively, movement of water through the system may fully or in partbe accomplished through the use of a gravity feed arrangement. Forexample, the water to be input to system 100 is located above system100, where gravity is used to move the water through the system.Further, in certain embodiments, a battery configuration is used tostore electricity generated by solar system 120. Then, power is suppliedto the various components on an as-needed basis, such as when solarsystem 120 is not generating electricity.

Still further, while solar system 120 is illustrated as the source ofpower in FIG. 1 in other embodiments, alternative power sources may beused alone or in conjunction with the solar system 120. One particularalternative configuration is a manual generator or dynamo, where theuser cranks the generator or dynamo to charge a connected electricalstorage device and/or to power the components directly. In thisembodiment, total reliance on the sun is therefore not necessary. Othersources of power which are represented by indicator 120 include powerfrom wind turbines and hydroelectric sources among others.

Additionally, certain safety features may be implemented in alternativedesigns. For example, pressure relief valves are selectively included toensure that water pressure within the system does not exceed a certainmaximum. Another safety feature that is implemented in variousembodiments is an automatic shutdown switch that recognizes themalfunctioning of components of the system, including but not limited tothe UV sterilizer. For instance, if a lamp in the UV sterilizer burnsout or malfunctions, this state is used as a signal to activate ashutdown switch which shuts down the system, such that unprocessed waterdoes not exit system 100.

Turning to FIG. 2, illustrated is a more detailed depiction of thetechnology of an electrocoagulation system that is used in system 100 ofFIG. 1. It is to be appreciated the design of FIG. 2 provides a generaldescription of the operation of electrocoagulation systems, and suchsystems are known to exist. Companies which supply EC systems includeLanda Water Cleaning Systems of Comas, Wash., Forever Pure of SantaClara, Calif., and Powell Water Systems Inc., Centennial, Colo., amongothers.

Electrocoagulation system 106 of FIG. 2 includes a DC power supply 200,wherein one side of power supply 200 is connected, via wire line 202, toa plurality of anodes 204 a-204 n. A second side of power supply 200 isconnected, via wiring 206, to a plurality of cathodes 208 a-208 n. Theanodes and cathodes are held within a container 210 which holds water212 (e.g., water 102 of FIG. 1) being processed. In this embodiment, atthe bottom of container 210, a magnetic stirring bar 214 is located inoperative connection to a magnetic stirring controller 216. Whenactivated, stirring bar 214 mixes water 212. If it is deemed desirableto monitor operation of electrocoagulation system 106, a current meter218 is placed in series with line 202 (or line 206), and if voltage ofelectrocoagulation system 106 is to be monitored, a voltmeter 220 isplaced in parallel across lines 202 and 206.

Another common type of coagulation process is achieved by use ofchemical coagulation. Similar to electrocoagulation, conventionalchemical coagulation is used to destabilize suspensions and to effectprecipitation of soluble metals species, as well as other inorganic andorganic species from aqueous streams, thereby permitting their removalthrough sedimentation or filtration. Alum, lime and/or polymers arecommon chemical coagulants used in such processes. Such conventionalchemical coagulation processes however involve adding significantamounts of chemicals to the water in a large basin or other containerand tend to generate large volumes of sludge with high bound watercontent that can be slow to filter and difficult to dewater.Electrocoagulation removes metals, colloidal solids and particles, andsoluble inorganic pollutants from aqueous media by introducing highlycharged polymeric metal hydroxide species. These species neutralize theelectrostatic charges on suspended solids and oil droplets to facilitateagglomeration or coagulation and resultant separation from the aqueousphase. The treatment prompts the precipitation of certain metals.

As shown in FIG. 2, an electrocoagulation system essentially consists ofpairs of conductive metal plates in parallel, which act as monopolarelectrodes. It furthermore uses a DC power source, a resistance toregulate the current density and a multimeter to read the currentvalues. The conductive metal plates are commonly known as “sacrificial”electrodes and can be of the same or of different materials, such as butnot limited to iron.

During electrolysis operation of the electrocoagulation process, thepositive side of the system undergoes anodic reactions, while thenegative side undergoes cathodic reactions. The polarity of the appliedvoltage is periodically reversed to sacrifice both electrodes moreuniformly. The released ions neutralize the charges of the particles andthereby initiate coagulation. The released ions remove undesirablecontaminants either by chemical reaction and precipitation, or bycausing the colloidal materials to coalesce, which can then be removedby flotation. In addition, as water containing colloidal particulates,oils, or other contaminants move through the applied electric field,there may be ionization, electrolysis, hydrolysis, and free-radicalformation which can alter the physical and chemical properties of waterand contaminants. As a result, the reactive and excited state causescontaminants to be released from the water and destroyed or made lesssoluble.

Returning attention to FIG. 1, once water 102 has been processed usingthe electrocoagulation system 106, the EC processed water 102 isprovided to maturation buffer tank 108. Due to the use of spiralseparator 110 in system 100, it is desirable to have the pin floc formedwithin buffer tank 108 to be aggregated to at least a particular cut-offsize. As will be explained in further detail, spiral separator 110 canbe adjusted to separate from the water, floc over a certain size.Therefore, it is desirable to grow pin floc within the maturation tankto at least that size such that it is at or above the cut-off size. Onediscussion of floc development in a maturation buffer tank, such as inthe present application, is described in U.S. patent application Ser.No. 12/234,373, “Method And System For Seeding With Mature Floc ToAccelerate Aggregation In Water Treatment Process.”

Having been processed in buffer tank 108, water 102 is then moved tospiral separator 110 for floc separation.

In one embodiment, the spiral separator may be constructed according tothe teachings of the patents and applications incorporated herein,including but not limited to the separator operates in some embodimentsas the spiral separators described, for example, in U.S. Publication No.2008/0128331 A1, having U.S. Ser. No. 11/606,460, filed on Nov. 20, 1006and entitled “Particle Separation and Concentration System,” U.S. Ser.No. 11/936,729, filed on Nov. 7, 2007 and entitled “Fluidic Device andMethod for Separation of Neutrally Buoyant Particles,” and U.S. Ser. No.11/936,753, filed on Nov. 7, 2007 and entitled “Device and Method forDynamic Processing in Water Purification.”

Turning to FIGS. 3, 4A, 4B, 5 and 6, concepts for a spiral separator,which is appropriate for use as the spiral separator 110 of the presentapplication are disclosed. It is understood that other embodiments ofthe spiral separator such as described in the cited andincorporated-by-reference applications are also applicable to thepresent application.

With reference to FIG. 3, a segment of a curved channel 300 showingvarious forces acting on a particle 302. Also, the velocity profile andthe pressure distribution are shown.

Analytic consideration for the flow in a curved channel is as follows.In this regard:

-   -   V=Flow velocity    -   p=Pressure    -   F_(cf)=Centrifugal force on the particle    -   F_(ΔP)=Force due to pressure differential    -   F_(vd)=Force due to viscous drag    -   R=Radius of curvature of the channel    -   η=Dynamic viscosity of the fluid    -   m=Mass of the particle    -   r=Radius of the particle assumed to be spherical    -   ρ=Density of fluid

The expressions for the centrifugal (∝³), transverse pressure driven(∝r²), and viscous drag forces (∝r) acting on the particle can beexpressed as follows:

$F_{cf} = {\frac{m\; V_{\theta}^{2}}{R} = {\rho\frac{4}{3}\pi\; r^{3}\frac{V_{\theta}^{2}}{R}}}$F_(Δ p) = p π r² F_(vd) = 6 π η rV_(r)

The particles will move outwards if F_(cf)>F_(Δp), or

${\rho\frac{4}{3}\pi\; r^{3}\frac{V_{\theta}^{2}}{R}} > {p\;\pi\; r^{2}}$${i.e.r} > {\frac{p}{\rho}\frac{R}{V_{\theta}^{2}}\frac{3}{4}}$

Equation (1) can be used to determine the lower bound for particle sizethat will move outwards for any given geometry, pressure and velocity offlow. Particles smaller than this lower bound will move inwards or

$r < {\frac{p}{\rho}\frac{R}{V_{\theta}^{2}}\frac{3}{4}}$

The distance of travel before a particle migrates across the flowchannel (transverse direction) is dependent on the relative magnitudesof F_(vd) and F_(Δp).

Also since F_(Δp)∝r² and F_(vd)∝r, larger particles will be moreaffected by the flow induced transverse pressure drop directed towardsthe inner surface.

The transverse pressure may be derived by considering peripheral flow ina concentric cavity where the parabolic profile fits:V _(θ) =V ₀(r−r ₁)(r ₂ −r)and r₁ and r₂ are the inner and outer radii, respectively. The radialPressure drop, p, is given by:

$p = {{\int_{1}^{2}{\frac{\rho\; V_{\theta}^{2}}{R}{\mathbb{d}r}}} = {V_{0}^{2}{\frac{\rho}{R}\left\lbrack {\frac{r^{5}}{5} - \frac{\left( {r_{1} + r_{2}} \right)r^{4}}{2} + \frac{\left. {r_{1}^{2} + {4r_{1}r_{2}} + r_{2}^{2}} \right)r^{3}}{3} - {r_{1}{r_{2}\left( {r_{1} + r_{2}} \right)}r^{2}} + {r_{1}^{2}r_{2}^{2}r}} \right\rbrack}}}$

The calculated velocity and pressure profiles are shown in FIGS. 4A and4B. The pressure is displayed as a function of distance from the innerwall, beginning from r₁ and increasing to r₂. The inward-directedpressure field (from the outside wall) is clearly evident.

The required flow length of the channels is designed to meet the channelwidth and flow velocity for the particle size range. The equation ofmotion in the radial direction for outward directed motion is given by:

${m\frac{\mathbb{d}V_{r}}{\mathbb{d}t}} = {{\frac{m\; V_{\theta}^{2}}{R} - {p\;\pi\; a^{2}} - {6{\pi\eta}\;{aV}_{r}}} = {\left( {\alpha - {\beta\; V_{r}}} \right)m}}$where $\alpha = {\frac{V_{\theta}^{2}}{R} - \frac{p\;\pi\; a^{2}}{m}}$$\beta = \frac{6\;{\pi\eta}\; a}{m}$

The solution to equation of motion is the radial velocity:

$V_{r} = {\frac{\alpha}{\beta}\left( {1 - {\mathbb{e}}^{{- \beta}\; t}} \right)}$with acceleration time-constant, τ, given as:

$\tau = {\frac{1}{\beta} = \frac{m}{6\;{\pi\eta}\; a}}$and terminal velocity of

$V_{\infty} = \frac{\alpha}{\beta}$

The corresponding relationships for inward motion where transversepressure is dominant and may be derived by changing the polarity of thecentrifugal and pressure driven forces in the equation of motion.

This transit time has to be considered together with sedimentation timegiven by:

$\tau_{s} = \frac{h}{V_{y}}$where h is channel height and V_(y) is given by

$V_{y} = \frac{{{\gamma 4}/3}\pi\; r^{3}\rho_{particle}g}{6\;{\pi\eta}\; a}$and γ is the buoyancy term given by:

$\gamma = \frac{\rho_{particle} - \rho_{fluid}}{\rho_{fluid}}$

For particle separation, these relations are used to design a device forthe desired particle size range. In this way, in one contemplated formof the presently described embodiments, a parallel array of collectionoutlets accumulate particles of the designed size range based on transittimes and transverse migration velocities.

In this regard, with reference now to FIG. 5, one form of a separationdevice 110 according to the presently described embodiments is shown.This form shows an expanding spiral channel 502 with increasing radiusof curvature. This geometry takes advantage of the rate of pressurechange: dp/dR∝1/R². In another form, the device may have a contractingspiral channel with decreasing radius of curvature for the side walls ineither case, the channel 502 evolves from inlet 504 into two separatechannels 506 and 508 (e.g., also referred to as channel #1 and channel#2) to respective outlets 510, 512.

An exploded view of the spiral separator device 110 of FIG. 5 is shownin FIG. 6. In one form, the width of the widest section of theseparation channel 502 is, for example, 10 mm and tapers to 5 mm nearthe inlet 504 and outlets 510, 512. The inlet 504 is near the center ofthe separator 110 and the outlets 510, 512 are near the outer perimeter.Particles move with the fluid but also migrate across the channelcross-section. In one form, the height of the channel structure varies,for example, from 0.5 mm to 2 mm. Each outlet 510, 512 selectivelycollects separated particles depending on the fluidic velocity.Particles are collected in channel #1 (506) and #2 (508) at low and highfluid velocity, respectively. Thus, the spiral separator separates waterflowing through, into at least two streams of water, a first stream ofwater having at least some particles (e.g., floc) removed, and thesecond stream of water including a concentrated amount of particles(e.g., floc).

The channels 502, 506 and 508 may be formed in a variety of manners,e.g., by cutting Acrylic sheets 600, 602 and 604 ( 3/16″ and 1/16″thickness) to the required dimensions using a laser cutter. The channelsare then cut in the sheet 604. In one form, sheets 600 and 602 form thetop and bottom covers and also provide holes for inlet 504 and outlets510, 512. Although not shown, two 500 μm thick silicone sheets may formthe fluidic seals at the two interfaces between the three Acryliclayers.

Notably, the presently described embodiments provide for particleseparation in a variety of manners. For example, depending on the flowrate, the particle separation may be driven by the centrifugal force orthe pressure that is created by the flow of fluid through the channel.In this regard, different outcomes result from the two different inletflow rates. In either case, particle separation occurs.

Turning to FIG. 7, depicted is a second particle separation embodimentfor neutrally buoyant particles. This figure is referred to for adescription of hydrodynamic separation where purely fluidic flow incurved channel structures create the necessary migration, focusing, anddiversion of a tubular band as the waste stream.

More particularly, in FIG. 7, a curved channel 650 (e.g. a curvedportion of a spiral) has a particle 652 flowing there through. As can beseen, asymmetric tubular pinch effects in the channel—created by variousforces—are shown. The forces include a lift force F_(W) from the innerwall, a Saffman force F_(S), Magnus forces F_(m) and a centrifugal forceF_(cf). It should be appreciated that the centrifugal force F_(cf) isgenerated as a function of the radius of curvature of the channel. Inthis regard, this added centrifugal force F_(cf) induces the slowsecondary flow or Dean vortex flow (shown by the dashed arrows) whichperturbs the symmetry of the regular tubular pinch effect. Particles areconcentrated in the inner equilibrium of the velocity contour (shown inthe dashed ellipses).

Thus, while the first particle separation embodiment requires densitydifference for centrifugal force to move suspended particles relative tothe fluid, this embodiment moves the fluid particles which creates aviscous drag on the neutrally buoyant suspension causing particles tomigrate to a new position where force equilibrium localizes them to formthe tubular band. Fluidic shear in straight channels is known togenerate lateral forces which cause inertial migration of particulates.Segre and Silberberg experimentally demonstrated the tubular pincheffect in a straight channel where neutrally buoyant particles migrateto form a symmetric band that is 0.6D wide, where D is the channeldiameter. In quadratic Poiseuille flow, three contributions haveexplained the lateral migration of a rigid sphere. The wall lift, F_(w),acts to repel particulates from the wall due to lubrication. The secondcontribution is the Saffman inertial lift towards the wall due to shearslip,F _(s)=6.46ηVaR _(e) ^(1/2)where η, V, a, and R_(e) are respectively, the fluid viscosity, averagechannel velocity, particle radius, and channel Reynold's number givenby:R _(e) =ρVD/ηwith ρ and D being the fluid density and hydraulic diameter of thechannel. The third is the Magnus force due to particle rotation towardsthe wall,F _(m) =πa ³ ρ{right arrow over (Ω)}×{right arrow over (V)}where {right arrow over (Ω)} is the angular velocity given by ΔV/r andΔV is the differential velocity across the particle. F_(w) dominatesnear the wall and achieves equilibrium with the combined effects ofF_(s) and F_(m) to confine particles in a band. Segré and Silberbergdeveloped a reduced length parameter to scale this tubular pinch effectin a simple form within a straight channel,

$L = {\left( \frac{\rho\;{Vl}}{\eta} \right)\left( \frac{a}{d} \right)^{3}}$where l is the actual channel length and d is the hydraulic channelradius. In curvilinear channel geometry, a centrifugal force modifiesthe symmetric tubular pinch effect. The fluid inertia from this forcecauses a secondary transverse flow or Dean vortex which is a doublerecirculation. The Dean number is a measure of the strength of thisrecirculation:D _(e)=2(d/R)^(1/2) R _(e)where R is the radius of curvature of the channel. Particles inmid-elevation migrate transversely outward with the Dean vortex, arerepelled by the wall lift, and continue to loop back along the top andbottom walls towards the inside wall. The combined Saffman and Magnusforces is large in comparison to the viscous drag of the Dean vortex soparticles are trapped in a force minimum located adjacent and closer toone side wall. At low flow rates, the band is closer to the inner sidewall. At high flow rates, the band migrates to a location adjacent theouter side wall.

So, it is apparent that the tubular band is formed as a function of atleast one of fluid viscosity, average channel velocity, particle radius,fluid density, hydraulic diameter of channel, angular velocity, anddifferential velocity across particles. Moreover, as noted above, oneaspect of the present innovation is to control the tubular band to beoffset from the center of the channel as a function of a radius ofcurvature of the spiral channel. So, the configuration and operation ofthe system is a function of the factors contemplated, for example, bythe generic expression

$L = {\left( \frac{\rho\;{Vl}}{\eta} \right){\left( \frac{a}{d} \right)^{3}.}}$These factors or parameters are highly scalable and will vary as amatter of application in the range from micro-scale devices tomacro-scale devices.

Returning attention again to FIG. 1, an optional filter 112 is insertedfollowing the spiral separator 110 to insure against abnormal operationconditions and/or feed water quality variations. A filter with theproper mesh rating to meet the required standards may be used. Duringnormal operation, the filter will require only infrequent back flush.

As previously described, water 102 with the floc removed is provided toUV sterilization system 114. It is to be understood that many UV systemsexist, and may be employed as UV sterilization system 114. For example,FIG. 8 provides a perspective view of an ultraviolet water disinfectionsystem which may be used as UV system 114 of FIG. 1. UV system 114 ofFIG. 8 comprises a water treatment chamber 700 having an inlet end 702including an inlet opening 704 to which is connected a suitable tube orconduit 706 for delivering water to treatment chamber 700. Chamber 700further includes an outlet end 708 having an outlet opening 710 to whichis connected suitable tube or conduit 712 through which the treatedwater is discharged. Treatment chamber 700 further comprises a lid 714which is hingedly mounted by means of a suitable hinge 716. The insidesurface of lid 714 is preferably a reflective material for reflectingthe ultra-violet radiation back downward into the water being treated.

UV system 114 further comprises a rack 718 for supporting a plurality oftube-type ultra-violet lamps 720 in a parallel spaced array.

Rack 718 is preferably constructed of materials which are notdeleteriously affected by prolonged contact with water. Furthermore,rack 718 is designed to be removably suspended from lid 714 of chamber700 so that it rests on the bottom surface of chamber 700 when lid 714is closed, but is lifted out of chamber 700 when lid 714 is raised. Asuitable power supply with wiring 722 for providing power to UV lamps720 is provided with automatic power switch 724 preferably affixed tothe outside of treatment chamber 700 so that the power to the systemautomatically shuts off when lid 714 is opened.

With the configuration of support rack 718 as shown and described, thearray of UV tubes is lifted from the treatment chamber 700 when lid 714is pivoted to an open position. This allows easy cleaning of theprotective tubes 726 which house UV lamps 720 and replacement of UVlamps 720. Furthermore, with this configuration, all the water passingthrough treatment chamber 700 by necessity passes through the array ofUV lamps, flowing around the lamps and therebetween to providesufficient exposure time of the water to the UV radiation to effectdisinfection of the water. Regardless of the depth of the water intreatment chamber 700, all the water passes through the array of lamps720, with a greater portion of each lamp being submerged as the liquidlevel becomes higher. Additionally, based on the angled orientation ofthe UV lamps, the UV lamps are in a wet/dry orientation during operationof the system wherein a portion of the lamps is submerged and a portionis not submerged. The nonsubmerged portion transmits UV radiationthroughout the box through the air and those rays are reflected backdown into the water by the reflective surface on the inside of lid 714.

Other UV sterilization systems which can be employed in the presentapplication from a variety of companies including UV Waterworks fromWaterHealth International Inc. of Irvine, Calif. and United IndustriesGroup Inc. of Newport Beach, Calif., among others. Additionally, thesterilization process of system 100 may be accomplished by use of othersterilization technologies such as by use of different irradiationtechnologies. Additionally, as previously mentioned, advanced oxidationtechniques using photocatalytic materials such as, but not limited to,TiO₂ can be used, either as surface coating of the inside of the spiralseparator 110, and/or as dispersion of a nanoparticles into the sourcewater.

Turning to FIG. 9, illustrated is a more detailed water treatment system800 in accordance with the present application.

System 800 includes solar (PV) power supply system 120 which convertssunlight into electricity which is in turn stored in battery storage802. The solar power supply system 120 is configured of multipleindividual solar panels, such as 120 a-120 n, arranged in an appropriateconfiguration such as parallel and/or serial arrangements to provide theamount of energy needed to run system 800. In an alternative embodiment,a manually operable generator or dynamo 804 is included to generatepower when sunlight is not available for conversion. An electrical powercontroller 806 is provided in operative connection to battery storage802 to control the energy provided to components of the integrated watertreatment system 800 of FIG. 9.

In operation system 800 receives source water 102 via use of an inputpump system 808 supplied with power from controller 806 at a suitableinlet (shown representatively) from an input water source that is, inone form, flowed through mesh filter 104. It should be appreciated thatmesh filter 104 is designed to filter out relatively large particlesfrom the input water. In this regard, the filter 104 may be formed of a2 mm-5 mm mesh material, although other sized filters may be used.

Water 102 which has passed through filter 104 is provided to thepreviously discussed electrocoagulation system 106. As illustrated inthis drawing, the electrocoagulation system is supplied with power,again, by controller 806. Water output from electrocoagulation system106 is then passed to the maturation buffer tank 108.

The output from buffer tank 108 is passed to spiral separator 110 whichhas a water (or effluent) output 510 (see FIG. 5). The output 510directs a water stream, which has been separated from the floc, to theoptional filtering mechanism 112 before the UV sterilization system 114.The output of the UV sterilization system 114 typically comprises thetreated potable water 118.

Spiral separator 110 has a second output 512 (FIG. 5) from which wastewater is passed. The waste water can be disposed of in an appropriatemanner.

Returning attention to the UV sterilization system 114 in the presentembodiment, it can be seen by FIG. 9 this unit is energized viacontroller 806 as with other components of system 800. UV sterilizationunit 114 is further configured with a safety switch 820 which isconnected to automatic power switch 724. In this design, the safetyswitch 820 senses a malfunction of the UV tubes 720 and relays thisinformation to controller 806. Controller 806 then shuts down operationof system 800 to ensure that improperly processed waste water does notbecome delivered to users as clean drinking water. It is to beunderstood the safety switch 820 is given as an example, and othersafety mechanisms may also be associated with other components of system800, such as but not limited to proper operation of theelectrocoagulation system and the spiral separator, among others.

System 800 also shows the use of pressure relief valves 822, 824, 826implemented to ensure proper water pressure in the system.

It is to be appreciated filter arrangements 104 and 112 may each becomprised on a single filter stage, or multiple filter stages, and eachare, in some embodiments, replaceable and/or alternatively able to beremoved, cleaned and reused.

Having described the system of FIG. 9 along with the more generaldescription of FIG. 1, with the details of FIGS. 2-7, it is understood asystem as developed according to the concepts and teachings describedherein will in some embodiments be designed to serve communities of 500to 1,500 people, which require approximately 35-75 gpd (i.e., gallonsper day) per person and the system (100 or 800) with a water treatmentrate of 100 Lpm (i.e., liters per minute). The system has severaladvantages to existing systems including a small footprint, and anefficient use of materials and lowered energy use. For example, by useof the electrocoagulation system, the cost and waste of chemicalcoagulation is avoided. Particularly, in comparing the aspects ofelectrocoagulation to conventional chemical coagulation,electrocoagulation is understood to operate and be maintained at a muchlower cost than conventional chemical coagulation. Electrodes arecompact, and replacement is required only when necessary. On the otherhand, in conventional chemical coagulation, only about 5.0% to 7.0% ofthe coagulation chemical added to a waste stream are often actually usedfor the coagulation process. The remaining percentage of the materialsare wasted and returned, possibly to the environment. It is also commonwhen using conventional chemical coagulation that the system may beoverdosed with the chemical coagulant, which requires cleanup prior todischarging the water back into the water supply, whereas in theelectrocoagulation only the needed electrode material is dissolved byelectrochemical processes.

Chart 1 below illustrates energy and cost comparisons betweenconventional chemical coagulation and electrocoagulation:

CHART 1 volume to treat (1000 gal) [V] 3.8 m{circumflex over ( )}3 ionconcentration needed (2 mM) [C_(i)] 2.00E−03 kmol/m{circumflex over( )}3 Faraday constant [F] 9.65E+07 C/kmol power cost [ΔC_(P)] 1.00E−01$/kWh mass coagulant mol weight cost fraction of cost [kg/kmol] [$/kg]valence coagulant [$/kg]¹ [M_(w)] [C_(w)] [z] [f] [DC_(C)] Al 27 2.4 35.70% 0.242 KAl(SO₄)₂*12(H₂O) Al 27 2.4 3 8.11% 0.242 Al₂(SO₄)₃*18(H₂O)Fe 55.8 0.8 2 20.64% 0.506 FeCl₃*6(H₂O) calculations based on a smallflow cell - resulting in small overall flow rate EC electrode area (900cm{circumflex over ( )}2)[A] 9.00E−02 m{circumflex over ( )}2 electrodespacing (0.4 cm) [d] 0.004 m flow rate (0.71/min)[q] 1.1667E−05 M{circumflex over ( )}3/s solution conductivity (0.85 mS/cm) 8.50E−02S/m [σ] time to treat volume [t] 325714.286 s (≈90 h) Al Fe Faradayresistance (d/σ = 0.471 cm{circumflex over ( )}2/mS) 0.5 0.2 W [P₀]current multiplayer [ΔI] 2 1 metal power mass [kg] cost [$] currentpower cost total cost [$] [m] [C_(m)] [A/m{circumflex over ( )}2][i][kW][P_(EC)] [$][C_(EC)] [C_(EC,tot)] Al 0.2052 0.49 75.0454 0.0065 0.060.55 Fe 0.4241 0.34 50.0303 0.0108 0.10 0.44 standard aggregation puremetal mass coagulant [kg] cost power power cost [m] mass[kg][m_(C)][$][C_(C)] [kW]²[P_(S)] [$][C_(S)] total cost [$][C_(S,tot)] Al 0.20523.6000 0.87 17.4679 1.75 2.52 Fe 0.4241 2.0547 1.04 17.4679 1.75 2.79¹From Penitencia water treatment plant May ′07 ²Mostly for initial rapidmix of coagulant ³Marin County Desalination Plant Estimate

A further beneficial aspect of the integrated system of the presentapplication is the use of a spiral separation device. This devicerequires low power for operation, and has low pressure consumptioncharacteristics, which is useful in a compact integrated system for theelectrical grid use. For example, in a system as described in thepresent application (i.e., for a 100 Lpm spiral unit), the spiralseparation device would require:ΔP=2 psiPower=20 Wwhere Power is the friction loss through the spiral separation deviceQ=100 L/minwhere Q is the flow rate.

Conventional water treatment systems include the sequential steps ofcoagulation, flocculation, and sedimentation; requiring long processtimes (hours) and large land space. This invention replaces thesedimentation step with spiral separation resulting in the much smallerfoot print necessary for a distributed (and mobile) water treatmentsystem. The rapid process (reduced from hours down to minutes), reducedchemical dosage (50%), and low power requirement all contribute to theconcept of a small foot print device that can be quickly deployed.

A further advantage of the present system is the implementation of a UVsterilization system. Such compact ultraviolet water disinfectionsystems which work on a small scale, are energy efficient, and provide alow-maintenance design. Typical small-scale sterilization units operateusing the equivalent of a 60 watt light bulb at a cost of as little as 4cents/ton of water treated, when treating 15 Liter/minute, which issufficient for a water treatment system designed to supply water to 500to 1,500 people.

Proper dosages in a UV system are dependent upon the matter beingsterilized. However, it is known that for sterilizing bacteria andviruses, a system would apply 2,000 to 8,000 μW-s/cm², and forsterilizing Giardia, Cryptosporidium, etc., the UV system would apply60,000 to 80,000 μW-s/cm². It is also to be understood suchsterilization units may use 6,000 times less energy than traditionalboiling techniques.

It is also known that UV light (240-280 nm) will deactivate DNA ofmicroorganisms. Microorganisms cannot, therefore, replicate and soonwill die. There is also no effect on the taste or smell of the water,and many times treatment takes as little as 12 seconds.

With attention to the solar considerations of the present watertreatment system, the device in accordance with the parameters set forthin this application, such as a 100 Lpm system, may require as much as 50KWH. And it is known:

-   -   For 250 W/m² solar panels        -   10 hour solar collection and energy storage, will require            50,000/10/250˜20 m², solar panels,        -   where 50,000 is the total electric power needed in a 24 hour            period; 10 is the number of hours for solar energy            collection, 250 is electrical power generated by 1 square            meter of solar panel; and        -   20 m² is the total area of solar panel that is required.    -   Then to power an electrocoagulation system with (Al electrodes)        the required power would be approximately:        -   37.89×0.024×24=22 KWH,        -   where 37.89 is the multiple of 1000 gal processed per day;            0.024 is the power needed to process 1000 gals; and 24 is            the 24 hour period of operation.    -   For operation of the spiral separator, the required power would        be approximately:        1 HP (20W+head loss)˜746×24=18 KWH,        -   where 20 W is friction loss through the separator; head loss            is pressure and friction losses through the piping; 746 is            wattage per HP; and 24 is the 24 hours of operation.    -   For operation of the UV Sterilization System, the required power        would be approximately        60W×(100/15)×24=9.6 KWH,        -   where 100 is the flow rate in liters/minute; 15 is designed            flow rate in liters/minute for the UV WaterWorks system; and            24 is 24 hours of operation.

Turning to FIG. 10, illustrated is a further embodiment of a standaloneintegrated water treatment system according to the present application.As mentioned above, conventional chemical coagulation processes havecertain drawbacks which work against their implementation in smallintegrated water treatment systems. However, FIG. 10 depicts anintegrated, small footprint water treatment system 900 which includesin-line chemical coagulation and flocculation for the generation ofaggregated floc particles within spiral channels of the spiral mixer810. In addition, to fluid shear, the relative narrow confines of thespiral channels allow for effective diffusion of chemicals as thediffusion length is of the order of the channel width. Whereasconventional water treatment systems employ relatively large coagulationand flocculation basins which extend the aggregation time. Thein-channel aggregation of floc particles is possible at least in partdue to this limited diffusion length. The present embodiment alsoprovides a customized shear rate performing a size-limiting function sothat dense uniform-sized aggregated floc particles are formed Theseuniformly-sized aggregated floc particles can aggregate rapidly in thebuffer tank to be separated without the need for downstreamsedimentation. Proof of concept experiments have shown that the moreefficient mixing and separation described allows a 50% reduction ofcoagulant dosage to achieve the same turbidity reduction capability ofconventional systems requiring extended sedimentation. Additionally,spiral mixer 810 may also operate as a spiral mixer-conditioner, wheremixing takes place in the channels of the turns operated at or above thecritical Dean number (at or greater than 150), and aggregationconditioning occurs in the channels of the turns where the operation isbelow the critical Dean number.

In exemplary system 900, input source water 102 is received at asuitable inlet, which in one form is a mesh filter 104. It should beappreciated mesh filter 104 is designed to filter out relatively largeparticles from the input source water. In this regard, the filter 104may be formed of a 2 mm-5 mm mesh material. Alkalinity is added in-linein the form of a base to the input source water after filtering by meshfilter 104 to adjust for pH throughout the process. Any suitable basemay be used. Coagulant is added to the input water after the alkalinitybase is added and prior to mixing in spiral mixer 810. Any suitablecoagulant is used.

Spiral mixer 810 receives the input source water, treated with thealkalinity, and the coagulant. The spiral mixer shown in FIG. 10 servesa dual purpose. First, it provides a flash mixing function where theincoming source water is angled at the inlet to cause chaotic mixingwhen the source water impinges on a lower spiral channel wall of spiralmixer 810. Secondly, custom shear is designed into the fluidic flow ratein the channel to achieve a shear rate which limits growth of loosefloc. The resulting floc particles are dense and uniform within a narrowsize range of 5-10 um. These dense, uniformly sized floc particlesensure rapid aggregation. The spiral mixer 810 has an output thatconnects to a buffer tank 108. The source water is held in the buffertank for a determined buffer time (e.g., in some cases about fourminutes) to allow for fluid impedance matching between spiral mixer 810and a spiral separator 110.

The output of the buffer tank 108 is connected to the spiral separator110 which has an effluent output 510. The effluent output 510 directseffluent separated out from the source water input to the spiralseparator to filtering mechanism 112. Output of filtering mechanism 112typically comprises treated water that may be further added upon by UVsterilization 114. Spiral separator 110 has a second output line 512 inwhich waste water travels. The waste water can be disposed of in anappropriate manner.

Spiral mixer 810 may take a variety of forms, including that describedin U.S. Ser. No. 11/936,753, filed on Nov. 7, 2007, entitled “Device andMethod for Dynamic Processing in Water Purification,” among others. Inthis regard, the spiral mixer may take a physical form substantiallysimilar to that of a spiral separator with some minor and/or functionalmodifications. Further, the angle θ of impingement is approximately 90degrees where the fluid is received would, for a spiral mixer, be tunedto create sufficient turbulence in the channel to mix, rather thanseparate, the particles of the source water (as noted above). Also, asnoted above, the growth of floc is controlled in the mixing state as aresult of shear forces.

It is to be appreciated that in certain instances devices and systems ofthe present application such as electrocoagulation units, solar panelsand/or sterilization units may be obtained from manufacturers asoff-the-shelf devices. It is understood to construct a cost-efficientstandalone integrated water treatment system according to the presentapplication, these off-the-shelf systems may be integrated into thiswater treatment system.

It will also be appreciated that various of the above-disclosed andother features and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also thatvarious presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

What is claimed is:
 1. A stand-alone integrated water treatment systemfor distributed water supply comprising: a filtered input for receivingand treating water; a coagulation system in operative connection withthe filtered input, wherein the water which has been filtered isprocessed by a coagulation process by the coagulation system to createpin floc suspensions in the water; a maturation buffer tank in operativeconnection with the coagulation system, wherein the pin floc isaggregated to a larger size in the water; a planar spiral separatorhaving a curved channel comprising side walls and top and bottom wallsperpendicular to the side walls, the curved channel being in operativeconnection with the maturation buffer tank, wherein the water isseparated into two water streams a first stream of water having amajority of the floc removed and a second stream of water which includesa concentrated amount of the floc, wherein separation within the channelis based on the curvature of the channel in combination with at leastone of velocity and pressure profiles within the channel, orhydrodynamic forces within the channel; a sterilization system inoperative connection with the spiral separator and configured to receivethe first stream of water and to perform a sterilization operation onthe first stream of water; an output for outputting the water from thesterilization system as potable water; and at least one power supply forproviding power to the stand-alone integrated water-treatment system. 2.The system of claim 1 further including a filtration arrangement inoperative connection with the sterilization system to receive the waterof the first stream of water from the spiral separator tank before ithas been sterilized by the sterilization system.
 3. The system of claim1 wherein the at least one power supply is a system in operativeconnection with at least one of the coagulation system, the maturationbuffer tank, the spiral separator, and the sterilization system.
 4. Thesystem of claim 1 wherein the coagulation system is anelectrocoagulation system.
 5. The system of claim 1 wherein thecoagulation system is a chemical coagulation system.
 6. The systemaccording to claim 1 wherein the spiral separator separates flocaccording to size.
 7. The system according to claim 1 wherein thematuration tank generates floc to a size of or larger than a cutoff sizeof the spiral separator.
 8. The system according to claim 1 wherein thespiral separator is configured to move floc at the cutoff size or abovethe cutoff size to the second stream of water.
 9. The system accordingto claim 1 wherein the coagulation system is an off-the-shelf system andthe sterilization system is an off-the-shelf system.
 10. The systemaccording to claim 1 wherein the at least one power supply is a solarpower supply and it provides all of the power needed to operate thesystem.
 11. The system according to claim 1 wherein the at least onepower supply is a wind turbine and it provides all of the power neededto operate the system.
 12. The system according to claim 1 wherein theat least one power supply is a hydroelectric power supply and itprovides all of the power needed to operate the system.
 13. The systemaccording to claim 1 wherein power from the at least one power supply iselectric power and is stored in a battery system, so the water treatmentunit can be operated independent of the operation of the power supply.14. The system according to claim 1 further including a spiral mixer inoperative connection with the coagulation system and the maturationbuffer tank, wherein water from the coagulation system is provided tothe spiral mixer, and water from the spiral mixer is provided to thematuration buffer tank.
 15. The system according to claim 14 where ashear rate in the spiral mixer is matched to a slow mix shear rate inthe maturation buffer tank to prevent breakup of the floc.
 16. Thesystem according to claim 14, wherein the spiral mixer includes havingan angled inlet configured to cause chaotic mixing when the water fromcoagulation system impinges on a lower spiral channel wall of the spiralmixer.
 17. The system according to claim 1, wherein the spiralseparation system and the sterilization system are combined, and thesterilization system is a UV sterilization system including TiO₂dispersed within the water, the dispersed TiO₂ being recovered by thespiral separator.
 18. The system according to claim 1, wherein thespiral separation system and the sterilization system are combined, andthe sterilization system is a UV sterilization system including TiO₂coated on inner surfaces of the spiral separator.
 19. The systemaccording to claim 1 where a shear rate in the spiral mixer iscustomized to produce dense floc of a given uniformity that aggregatesrapidly in the maturation buffer tank.
 20. The system according to claim1 wherein flow length of the channel of the planar spiral separator isdesigned to meet channel width and flow velocity for a predeterminedfloc size range.
 21. The system according to claim 1 wherein the rate atwhich water is treated is 100 liters per minute.
 22. A stand-aloneintegrated water treatment system for distributed water supplycomprising: a filtered input for receiving and treating water; acoagulation system in operative connection with the filtered input,wherein the water which has been filtered is processed by a coagulationprocess by the coagulation system to create pin floc suspensions in thewater; a maturation buffer tank in operative connection with thecoagulation system, wherein the pin floc is aggregated to a larger sizein the water; a spiral separator having a curved channel cut into asheet of material, with a height of the channel approximately between0.5 mm to 2 mm, the spiral separator in operative connection with thematuration buffer tank, wherein the water is separated into two waterstreams a first stream of water having a majority of the floc removedand a second stream of water which includes a concentrated amount of thefloc, wherein separation within the channel is based on the curvature ofthe channel in combination with at least one of velocity and pressureprofiles within the channel, or hydrodynamic forces within the channel;a sterilization system in operative connection with the spiral separatorand configured to receive the first stream of water and to perform asterilization operation on the first stream of water; an output foroutputting the water from the sterilization system as potable water; andat least one power supply for providing power to the stand-aloneintegrated water-treatment system.
 23. The system according to claim 22,wherein the curved channel of the spiral separator further includes atop cover and a bottom cover.